The group of 40 terrorists were reported to have been killed by the plague at a training camp in Algeria earlier this month.

It was initially believed that they could have caught the disease through fleas on rats attracted by poor living conditions in their forest hideout.

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But there are now claims the cell was developing the disease as a weapon to use against western cities.

Experts said that the group was developing chemical and biological weapons.

Dr Igor Khrupinov, a biological weapons expert at Georgia University, told The Sun: "Al-Qaeda is known to experiment with biological weapons. And this group has direct communication with other cells around the world.

"Contagious diseases, like ebola and anthrax, occur in northern Africa. It makes sense that people are trying to use them against Western governments."

Dr Khrupinov, who was once a weapons adviser to the Soviet president Mikhail Gorbachev, added: "Instead of using bombs, people with infectious diseases could be walking through cities."

It was reported last year that up to 100 potential terrorists had attempted to become postgraduate students in Britain in an attempt to use laboratories.

Ian Kearns, from the Institute for Public Policy Research, told the newspaper: "The biological weapons threat is not going away. We're not ready for it."